U.S. patent number 4,338,489 [Application Number 06/119,497] was granted by the patent office on 1982-07-06 for headphone construction.
This patent grant is currently assigned to AKG Akustische u. Kino-Gerate Gesellschaft m.b.H.. Invention is credited to Rudolf Gorike.
United States Patent |
4,338,489 |
Gorike |
July 6, 1982 |
Headphone construction
Abstract
In a diaphragm arrangement for electroacoustical transducers, in
particular for headsets, one or more diaphragms lie in one plane
which extends in the immediate proximity of the user's external ear
and preferably parallel to the tangential plane of the user's
external ear. In order to enable the use of the headset to better
discern direction and distance by hearing, the diaphragm is divided
into several coherent, preferably stripshaped sections or composed
of several, preferably stripshaped part diaphragms which are
adjacent or follow each other in that particular direction in which
the user's ear is to locate the direction of sound incidence in the
use position. Each diaphragm section or each part diaphragm is
provided with a separate drive element or system, there being
provided, at least between drive elements or systems of two
diaphragm sections or part diaphragms following each other in the
sense of the required direction of sound incidence, an element
delaying the transmit time of the signals and/or a delay
circuit.
Inventors: |
Gorike; Rudolf (Vienna,
AT) |
Assignee: |
AKG Akustische u. Kino-Gerate
Gesellschaft m.b.H. (AT)
|
Family
ID: |
3505134 |
Appl.
No.: |
06/119,497 |
Filed: |
February 7, 1980 |
Foreign Application Priority Data
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Feb 12, 1979 [AT] |
|
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1029/79 |
|
Current U.S.
Class: |
381/117; 381/191;
381/371; 381/373; 381/408; 381/74 |
Current CPC
Class: |
H04R
1/403 (20130101); H04R 1/1075 (20130101); H04R
9/047 (20130101); H04R 1/2834 (20130101) |
Current International
Class: |
H04R
9/04 (20060101); H04R 1/32 (20060101); H04R
1/10 (20060101); H04R 1/40 (20060101); H04R
9/00 (20060101); H04R 003/00 (); H04R 009/06 ();
H04R 019/04 () |
Field of
Search: |
;179/156R,111R,115.5PV,182R,182A,1R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2335201 |
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Jun 1975 |
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DE |
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1454121 |
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Sep 1966 |
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FR |
|
50117531 |
|
Mar 1977 |
|
JP |
|
Primary Examiner: Stellar; George G.
Attorney, Agent or Firm: McGlew and Tuttle
Claims
What is claimed is:
1. An electroacoustic headphone transducer for producing sound
having discernable frontal direction and distance qualities with
respect to the user comprising, means defining a diaphragm with a
membrane extending in a plane and positionable in a use position in
close proximity to the external ear of a user, said diaphragm means
defining a diaphragm being divided into a plurality of adjacent
coherent sections disposed in succession substantially along a path
across the user's external ear from front to back, each section
energizable by an audio signal corresponding to the sound, a
support housing for supporting said diaphragm in the use position
which is substantially sound permeable, and means connected to said
sections for applying the audio signal to said sections, said audio
signal means applying the signal to a succeeding one of said
sections along said path with a delay with respect to the signal
applied to a preceeding one of said sections so that said signal
propagates unidirectionally from one section to a succeeding
section in said path to simulate the direction quality of the sound
and corresponding audio signal as it reaches the user's external
ear, the sum of all such delays not exceeding 0.3 ms, there being
substantially no reflecting surfaces behind said diaphragm as
viewed from the user's ear.
2. An electroacoustic transducer according to claim 1, wherein said
plurality of diaphragm sections are stripshaped and disposed one
next to the other.
3. An electroacoustic transducer according to claim 2, wherein each
of said diaphragm sections comprises separate parts of a single
diaphragm.
4. An electroacoustic transducer according to claim 2, wherein said
diaphragm sections comprise a plurality of separate diaphragm
parts.
5. An electroacoustic transducer according to claim 1, further
including a separate areal acting drive unit for each of said
diaphragm sections each connected to said means for applying the
audio signal.
6. An electroacoustic transducer according to claim 1, further
including at least one moving coil moving in an air gap permeated
by magnetic lines of force for each of said diaphragm sections.
7. An electroacoustic transducer according to claim 1, wherein said
means for applying the audio signal provides a delay for the audio
signal applied to the succeeding one of said diaphragm sections is
within the range of between about 0.035 ms and 0.28 ms.
8. An electroacoustic transducer according to claim 1, comprising
two of said diaphragm sections, one of said diaphragm sections
positionable, with the transducer in the use position, adjacent an
earlobe area of the external ear of a user and the other of said
diaphragm sections disposed adjacent the rear edge of the external
ear of the user, the delay for the audio signal applied to the
succeeding one of the diaphragm sections being in the range of
between 0.14 ms to 0.2 ms.
9. An electroacoustic transducer according to claim 8, wherein said
diaphragm sections adjacent the rear edge of the external ear of
the user receives the signal with the delay and is disposed at an
angle with respect to a tangential plane of the external ear of the
user.
10. An electroacoustic transducer according to claim 1, wherein
said support housing defines a cylindrical shaped coupling space
when in position enclosing the user's ear, the front side of which
is occupied by one of said diaphragm sections having an undelayed
audio signal applied thereto, and a rear side formed another of
said diaphragm sections for receiving the audio signal with delay
of approximately 0.28 ms, and with a bottom formed by several
additional ones of said diaphragm sections which receive the signal
with a successive delay of about 0.035 to 0.07 ms from front to
rear.
11. An electroacoustic transducer according to claim 1, further
including at least one passive diaphragm portion for closing a
coupling space with the head of the user to avoid sound reflection
in the coupling space.
12. An electroacoustic transducer according to claim 1, wherein
each of said diaphragm sections of a single encapsulated
transducer, with the sections disposed one behind the other in said
support housing.
13. An electroacoustic transducer according to claim 12, wherein
said support housing comprises an acoustically ineffective frame
with a friction resistance whereby reflection of sound is
avoided.
14. A method of reproducing sound having a discernable front
directional and distance quality, with respect to the user, with an
audio signal comprising, positioning a diaphragm supported by a
housing in a plane in close proximity to the external ear of a
user, the diaphragm being divided into a plurality of adjacent
coherent sections disposed in succession substantially along a path
across the user's external ear from front to back, activating a
first diaphragm section of the diaphragm along the path in
alignment with the direction quality, activating a second
immediately adjacent and successive diaphragm section along the
path with the same audio signal which has been delayed by a
selected time period, the total delay over all sections selected to
be less than 0.3 ms, the housing being selected to be substantially
sound permeable and there being substantially no reflecting
surfaces when viewed from the user's ear behind the diaphragm, the
audio signal propagating with delay unidirectionally from diaphragm
section to diaphragm section along the path.
Description
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a membrane arrangement for
electroacoustical transducers, in particular for headsets, in which
one or more diaphragms lie in one plane when the transducers are in
a use position, which plane extends in the immediate proximity of
the user's external ear and preferably parallel to the tangential
plane of the ear.
Headsets of this design are generally preferred at present. They
are characterized by their good frequency response and small
distortion factor. It was not yet possible however, despite all
efforts, to eliminate another deficiency inherent in most headsets
generally, namely the fact that direction and distance discernment
by hearing with headsets usually does not conform to reality.
Generally, a disturbing effect becomes noticeable in that the
acoustic event does not become audible in front of the headset user
as it should be, but more or less vaguely on the side, in the back,
or raised out of the horizontal plane (elevation). This is
attributable to the fact that when listening with headsets, the
signals at the eardrum do not coincide with those perceived in
actual live and free listening. Even slight deviations result in
incorrect sound location fixing in the ear.
Essentially, the position of the diaphragm of a headset, relative
to the natural direction of incidence of the sound waves is
decisive, for when the headset is worn, the diaphragm is usually in
a plane extending roughly parallel to the external ear so that the
sound waves are radiated by the headset diaphragm approximately
perpendicularly to the natural direction of incidence. To remedy
this deficiency, it has already been suggested to arrange a
diaphragm in such a way in the headset that the diaphragm is
positioned, when in use, about perpendicular to the lateral
direction of incidence, and in front of the user's external ear.
Such an arrangement, however, has the disadvantage that the
coupling space between diaphragm and ear becomes relatively large,
which has an unfavorable effect at least on the efficiency of the
headset and results in a loss in certain high frequency ranges.
The physical processes in sound transmission from a diaphragm to
the ear with the interposition of a coupling space are expressed in
the following theorem:
In the low frequency range from about 50 to 300 Hz the diaphragm
mass and the restoring force due to the radial tension or the
retention system furnishes a resonance which is increased to 1000
to 3000 Hz by the restoring force of the coupling space. Below this
frequency range the diaphragm operates elastically inhibited, i.e.
with constant amplitude at constant driving force, whereby
frequency-dependent signals originate at the eardrum, as the
external ear has influence in this range. Above this range, the
amplitude of the diaphragm would drop, were it not for the
directional radiation due to the size of the diaphragm. With a
diaphragm area of 35 to 40 cm.sup.2 , a mass of about 0.015 g, and
a small coupling space, into which the outer ear projects freely,
the transition is gapless.
SUMMARY OF THE INVENTION
It is an object of the present invention to create a diaphragm
arrangement for electroacoustical transducers, in particular for
headsets, which enables the user of a headset to hear and perceive
direction and distance better. The basic concept of the invention
is to drive a diaphragm or juxtaposed part diaphragms successively
with a delay so that, in conjunction with undisturbed external ear
action, those audio signals are generated by the device correspond
to sounds which occur when listening freely, particularly when the
sound comes from the front. The problem is solved in concrete form
in that the diaphragm is divided into several coherent, preferably
stripshaped sections or is compsed of several, preferably
stripshaped part diaphragms which are adjacent to or succeed each
other in that particular direction in which with the device, the
ear is to locate the direction of sound incidence, and each
diaphragm section or each part diaphragm is provided with a
separate drive element system, there being provided, at least
between drive elements or systems of two diaphragm sections or part
diaphragms following each other in the sense of the required
direction of incident sound, an element for delaying the transit
time of the signal and/or a delay circuit.
The diaphragm arrangement according to the invention makes it
possible to keep the coupling space between ear and diaphragm small
on the one hand, and to drive the successive diaphragm sections or
the successive part diaphragms in a time differentiated manner, on
the other hand, so that the transmitted acoustic event is fed to
the ear in a manner corresponding to a frontal direction of
incidence, of the live sound, despite the diaphragm plane being
roughly parallel to the external ear plane. The time delay
difference between the individual, successive sections or part
diaphragms are proportioned so that the acoustic event reproduced
by the headset, i.e. the sound energies emitted by the sections or
part diaphragms, correspond to those occurring according to the
Huygen-Fresnel principle at the outer ear when listening to the
actual sound freely. This principle states that every point of any
wave field can be conceived as a spherical wave. Transferred to the
headset diaphragm this means that the invidividual diaphragm
sections or part diaphragms transmit time-delayed sound waves,
which is accomplished in the invention in that the sound radiation
from one diaphragm section to the other or from one part diaphragm
to the other is delayed according to the propagation time in the
free or actual sound field.
Assuming, in frontal sound incidence, the distance from the front
to the rear edge of the external ear to be 5 cm, the resultant
propagation time across the ear is about 0.14 ms. By splitting the
diaphragm into, for example, four stripshaped sections or part
diaphragms, the time delay between two successive sections or part
diaphragms is between 0.035 ms and 0.07 ms. Any number of diaphragm
sections or part diaphragm, of course, is possible, each driven
with corresponding delay. For economic and mechanical reasons,
however, it is expedient to restrict the number of diaphragm
sections or part diaphragms to four or five with at least two being
used.
To obtain the small delay differences between the successive
diaphragm sections or part diaphragms the known modules of the
RC-type or the RL-type are already sufficient. Of course, other
ways and means of group time delay may also be used, such as those
known from analog technology and also from digital technology (e.g.
the bucket chain circuit). If applicable, the signal amplitude can
be influenced at the same time, and a predetermined frequency
response can also be given to the delay element or delay circuit to
reproduce actual directional sound as closely as possible. But of
essential advantage for achieving the effect according to the
invention, namely the possibility of "frontal locating" when using
headsets is the division of the diaphragm area into several
parallel, e.g. vertical in use position, sections or strips
successively driven with time-delay according to the propagation of
the sound wave in the free sound field. Either the orthodynamic or
the electrostatic principle is particularly well suited as a drive
system, but moving coil systems serve the purpose also. Although
the problem of "frontal locating" when listening to acoustic events
with a headset is the primary objective of the invention, the
proposed arrangement can also be utilized for other acoustic
effects such as when listening to acoustic events transmitted
quadrophonically where the purpose is to simulate, in the headset,
the sound effects on the external ear which are direction-dependent
when listening freely or to live sound. By time-variable sound
radiation of the individual diaphragm sections or part diaphragms,
it is possible to vary almost arbitrarily the direction of sound
wave incidence in the headset, or to simulate simultaneously
correspondingly different directions of incidence of different
acoustic events.
So that the diaphragm arrangement according to the invention can
become fully effective, it is assumed that neither it nor any
surfaces in its immediate vicinity are in a position to reflect
sound. For, as has already been explained in the Austrian patent
applications 669/77 and 6285/77, surfaces as small as cm.sup.2, in
the vicinity of the ear entrance or 2 cm.sup.2 in the area of the
external ear, will cause linear signal distortions at the eardrum
which will not only falsify the sound fixation, but also cause the
"in the head localization effect". To prevent such undesired
effects, an extremely thin diaphragm material of a thickness from
20 to .mu.m is used in the invention, and the diaphragm or the part
diaphragms are mechanically clamped only under as little tension as
required to prevent the material from forming waves. In addition,
very low natural resonances, ranging between 50 to 200 Hz, can be
realized in this manner. Additional measures known in the headset
industry, such as the use of passive diaphragms to linearize the
frequency response, the application of friction resistance in the
area of the diaphragm surface may, if this creates no
sound-reflecting surfaces, be combined without difficulty with the
diaphragm arrangement according to the invention, and this may,
under certain circumstances, even intensify the effect according to
the invention.
Accordingly, an object of the present invention is to provide an
electroacoustic transducer particularly for a headphone or headset
comprising means defining a diaphragm with a membrane extending in
a plane and positionable in close proximity to the external ear of
the user, the means defining a diaphragm being divided into a
plurality of adjacent coherent sections disposed in succession,
each energizable by an audio signal, and means connected to the
sections for applying the audio signal to the sections with the
signal applied to a succeeding one of the sections with a delay
with respect to the signal applied to a previous one of the
section.
A further object of the present invention is to provide an
electroacoustic transducer which is simple in design, rugged in
construction and economical to manufacture.
A further object of the present invention is to provide a method of
reproducing a sound having a directional quality with an audio
signal which has a directional quality comprising, activating a
first diaphragm section of an electroacoustic transducer adjacent a
part of a user's ear with an audio signal, and activating a second
diaphragm section of the electroacoustic transducer adjacent the
first diaphragm section and adjacent a second part of the user's
ear which is adjacent the first part of the user's ear with the
audio signal which has been delayed by a selected time.
The various features of novelty which characterize the invention
are pointed out with particularity in the claims annexed to and
forming a part of this disclosure. For a better understanding of
the invention, its operating advantages and specific objects
attained by its uses, reference is made to the accompanying
drawings and descriptive matter in which preferred embodiments of
the invention are illustrated.
DESCRIPTION OF THE DRAWINGS
In the Drawings
FIG. 1 is an exonometric projection of a human ear on the portion
of a head of a user of the headset showing the travel direction of
a sound wave in time as it passes various parts of the ear;
FIG. 2 is a schematic perceptive view of a diaphragm according to
the invention which is divided into stripshaped sections.
FIG. 3 is a cross-sectional top view of an electrostatic transducer
according to one embodiment of the invention and arranged in
relationship to the ear of a user;
FIG. 4 is a side elevational view of the embodiment of the
electrostatic transducer shown in FIG. 3;
FIG. 5 is a top sectional view similar to FIG. 3 of another
embodiment of the invention in which the diaphragm sections are
driven orthodynamically or thadynamically;
FIG. 6 is a side elevational view of the membrane used in the
embodiment of FIG. 5;
FIG. 7 is a view similar to FIG. 5 of another embodiment of the
invention utilizing at least one additional diaphragm or diaphragm
section;
FIG. 8 is a view similar to FIG. 5 of another embodiment of the
invention utilizing a coupling space in which a diaphragm is also
assembled for the front of the headset;
FIG. 9 is a view similar to FIG. 5 of a still further embodiment of
the invention utilizing at least one passive diaphragm;
FIG. 10 is a circuit arrangement for providing a time delay in
accordance with the invention utilizing an orthodynamic drive
system;
FIG. 11 is a view similar to FIG. 10 of a circuit utilized for an
electrostatic system;
FIG. 12 is a circuit arrangement for achieving the invention
providing a phase shifting effect in the form of a bridge circuit
or cross circuit to produce the time delay;
FIG. 13 is a circuit similar to FIG. 12 of another embodiment of
the invention;
FIG. 14 is a view similar to FIG. 5 of a simplified version of the
invention;
FIG. 15 is a perspective view of a disc shaped transducer used in
accordance with another embodiment of the invention; and
FIG. 16 is a side perspective view an embodiment of the invention
utilizing the disc shaped transducer of FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A planar sound wave front coming from the line or direction of
vision of a user, reaches the front 4 of the user's external ear 1,
shown in FIG. 1 in exonometric projection and forming part of the
user's head 2. According to the previously mentioned Hygens-Fresnel
principle, therefore, a spherical wave is released at the front
edge 4 of the ear. The wave front propagates and generates another
spherical wave at an ear part 5 which is reached in the propagation
direction of the sound wave about 0.035 ms later. This process
continues over the entire width of the ear, and after about 0.14
ms, the sound wave has reached the rear edge 6 of the external ear.
Now, in order to simulate in the ear an at least similar process
when reproducing an acoustical event by means of a headset, a
diaphragm, such as one divided into stripshaped sections as shown
in FIG. 2, is used according to the invention. Each one of the
sections 8 to 12 of the diaphragm 7 has its own drive system. The
system assigned to the first diaphragm section 8, or the one
located in the front position when the device is in use receives
the signal without delay, whereas the second section 9 already
receives the signal delayed by 0.035 ms, which time difference is
also provided between it and the next section 10. The signal
transmission is also delayed in the same manner between the
sections 10, 11 and 11, 12 respectively, resulting in a mixture
delay of 0.14 ms over the entire diaphragm width. This corresponds
to the transit time of a sound wave from the front to the rear edge
of the human ear.
FIG. 3 shows the diaphragm arrangement according to the invention
in an electrostatic transducer in a use position, as viewed from
the top. A diaphragm 13 is clamped under slight tension in a frame
22 between the electrodes 14 to 21 arranged in pairs. The
electrical connections coordinated with each electrode pair are
marked 14a to 21a. In the sense of what was said above, the
electrical signal is fed to them delayed by a certain amount each.
FIG. 4 is a side plan view of the electrode arrangement provided in
the transducer according to FIG. 3. The electrodes are electrically
insulated from each other and provided with numerous holes (not
shown) to let the sound pass in as unhindered a manner as possible.
One embodiment and example of the invention, in which the
electroacoustical transducer works by the orthodynamic principle is
shown in FIG. 5 in a top view. A thin diaphragm 13' is provided
with printed conductors and clamped under slight tension between a
number of magnetic pole rods 23 on the one hand and 24 on the
other. The wiring of the printed embodiments on the diaphragm is
shown in FIG. 6. Essentially, they represent a number of parallel
flat coils 25 to 29 whose ends 30 to 39 are led to the diaphragm
edge, forming electrical terminals.
As already mentioned at the outset, bringing about the effect
according to the invention depends, among other factors, on the
avoidance of sound-reflecting surfaces in the proximity of the ear
entrance and/or the external ear. Embodiment examples meeting this
requirement are shown schematically in section in FIGS. 7 to 9, for
instance. It is provided, in the embodiment example according to
FIG. 7, that the stripshaped diaphragm sections or the stripshaped
part diaphragms of transducers be driven by the electrostatic
principle. The diaphragm plane extends, as shown in FIG. 7,
approximately parallel to an imagined plane which is tangent to the
ear. This results in the distance between head and diaphragm holder
in front, i.e. in the ear lobe area, being smaller than in the
rear, which leads to the coupling space being wedgeshaped. Now, in
order to prevent the reflection of sound waves from the coupling
space wall forming the backside, this wall is replaced by an
electrostatically driven diaphragm 41. The wall frame is formed by
latticeshaped electrodes 70 on both sides of the diaphragm 41. This
diaphragm and the adjacent stripshaped diaphragm with the
electrodes 42 are operated at the maximum delay of 0.14 ms, whereas
the sections or part diaphragms according to FIG. 2 operate with
staggered delay. To create no additional reflecting surfaces
through the ear cushion 40, it is designed here as well as in the
other embodiment examples as flat as possible.
In the embodiment example shown in FIG. 8, the coupling space is
roughly of canshaped or cylindrical design. This makes it possible
to assemble a diaphragm also on the front side of the coupling
space, i.e. in the ear lobe area, which membrane receives the
signal undelayed, as does the first stripshaped diaphragm section
or the first stripshaped part diaphragm. The subsequent diaphragm
sections or part diaphragms receive the signal with a delay of
about 0.035 ms each relative to the preceding one. As at the front
of the coupling space so also at its rear a diaphragm is inserted,
the delay of which amounts to about 0.28 ms versus the undelayed
diaphragm. The acoustical event is so transformed by this measure
as though it were perceived with enlarged external ears, making it
possible to locate the sound even more drastically than usual.
Another embodiment example in which the orthodynamic principle is
provided for driving the active diaphragm sections or stripshaped
part diaphragms is shown in FIG. 9. The diaphragm 45, divided into
stripshaped sections or the stripshaped part diaphragms (not
shown), are disposed between mutually parallel, magnetic pole rods
46. As before, the diaphragm sections are driven with staggered
delay. The wedgeshaped coupling space is closed off in the rear not
by a rigid wall, but by a passive diaphragm 43 which may be damped
by a friction resistance 44. This passive diaphragm 43 makes it
possible to influence the headset's frequency response. At the same
time, reflections in the coupling space are suppressed by this
measure. By the same token, surfaces limiting the coupling space on
top and bottom in the use position of the headset can be active
and/or passive diaphragms. Behind the diaphragms, as viewed from
the ear, however, no reflecting surfaces should be present.
Accordingly, the housing of each headset shell must be
sound-permeable to a great extent, such as in the case with a wire
cloth or wire mesh.
The operation of the diaphragm arrangement according to the
invention requires transit time-delaying devices and/or circuits.
One expedient possibility for an orthodynamic drive system is shown
in FIG. 10. The transit time delay for the individual diaphragm
sections or part diaphragms is accomplished here by means of a coil
75 provided with appropriate taps. The audio signal is applied to
terminals 75a, 75b. The conductors 25 to 29 of the diaphragm
sections are represented in the wiring diaphragm by ohmic
resistors, which by and large corresponds to reality. The
conductors 25 to 29 are connected to the taps of the coil 75 so
that the stepwise delay of the signal transit time matches that of
the natural one when a wave front travels across the ear from front
to back. The analogous arrangement when using the electrostatic
transducer principle, is shown in FIG. 11. The electrodes 72, 73
are disposed in pairs on both sides of the diaphragm plane 71. They
are respectively connected to taps of the ohmic resistors 46, 47
and, due to their natural capacitance in conjunction with the ohmic
resistance, they form RC circuits, same as the part sections of the
coil in the previously described embodiment example formed
transit-time delaying RL circuits. The amplitude weakening caused
by the delay circuits can be made up for by appropriate
countermeasures. For instance, when using the orthodynamic
principle, the magnetic flux of the various drive systems may be
varied and/or the ohmic resistance of the conductors may be
different. When using the electrostatic principle, the amplitude
lowering effect of the delay arrangement can be counteracted by
different electrode spacings and/or different D.C. voltages.
Paralleling resistors to the conductors of orthodynamic transducers
or paralleling capacitances to the electrode pairs of electrostatic
transducers may also be used for amplitude balancing. Apart
therefrom, ohmic losses in delay circuits may be precluded to a
large degree if designed as bridged circuits, cross circuits, or
differential circuits. Corresponding examples are shown in FIGS. 12
and 13. In conjunction with the capacitors 52 and 53, the coils 48,
49 and 50, 51 of the circuit arrangement shown in FIG. 12 furnish
an exclusively imaginary contribution to the complex damping.
The example according to FIG. 13 involves cross circuits, the coils
54, 55 and 56, 57, respectively, being arranged in their
longitudinal direction while the capacitors 58, 59 and 60, 61
respectively, lie in the cross arms. Such delay arrangements may be
assembled inside the headset housing as well as outside, i.e.
separated from it. In addition, bucket chain memories or other
digital, actively working arrangements may be employed in the
diaphragm arrangement according to the invention instead of passive
delay circuits.
Finally, a very simple embodiment example of the invention is shown
diagrammatically in FIG. 14. Replacing a larger number of
stripshaped diaphragm sections or part diaphragms are here two
diaphragms only. The diaphragm 63, located in front in the top
view, is operated without delay whereas the diaphragm 64 disposed
at an angle on the rear side of the coupling space, radiates the
signal with a delay of about 0.2 ms. It is immaterial for the
function of the arrangement whether the diaphragms are driven
orthodynamically or electrostatically. Here too, prerequisite for
the occurrence of the effect according to the invention due to the
time-shifted action of the sound waves of a signal upon the
external ear is the prevention of sound-reflecting surfaces in the
coupling space in the proximity of the ear. To achieve good headset
efficiency it is necessary to keep the coupling space as small as
possible.
Another simplified embodiment example is shown in FIG. 15 and FIG.
16. Assembled to a disc 65 are two preferably disc-shaped
transducers 66, 67 which may be driven electrostatically,
orthodynamically, piezoelectrically or by moving coil. The disc 65
is completely coated with an acoustic friction resistance 68 or
forms, itself, an acoustic friction resistance by being made of
sintered material, for instance. As FIG. 16 shows in section, the
circumaural cushion 69 is disposed circling the disc 65. A
completely perforated and therefore acoustically ineffective
housing 74 provides mechanical protection and physical shape
without reflecting sound waves radiated by the rear side of the
transducers 66, 67. The transducer located in front relative to the
external ear is operated without time delay while the transducer
behind it is operated with a time delay of about 0.14 to 0.2 ms.
Otherwise, the same prerequisites as described for the embodiment
example according to FIG. 14 apply to this simple embodiment
example of the invention as regards its perfect functioning.
While specific embodiments of the invention have been shown and
described in detail to illustrate the application of the principles
of the invention, it will be understood that the invention may be
embodied otherwise without departing from such principles.
* * * * *